Found this bug years ago which sv_gameplayfix_q1bsptracelinereportstexture cvar will cure and happens only in dedicated server mode, but I was curious if a mapper could tell me if there is something special about the brushes / planes on the maps that show this problem in those specific areas? In the video , e1m1 has the issue near the doors, and on e1m4 the area seems to be all above and below the bridge over the small pool of water. Do these brushes have any similarity?